Operating Instructions
Chapter
3
CLX 490
8 009 237/0000/07-05-2002
©
SICK AG · Division Auto Ident · Germany · All rights reserved
3-5
Product description
3.2.1
Autofocus function
The autofocus function enables the CLX to detect the distance of an object during the read-
ing process, without the need for external sensors, and then adjust the focus position auto-
matically to the reading plane of the bar code. In order to do so, the CLX measures the
object distance each time in its reading field in front of the reading window and internally cre-
ates a distance profile. Following this, it positions the focus on the object.
3 operating modes are provided for various applications:
•
Minimum distance:
the CLX focuses on the minimum distance in the distance profile
and ignores the background in the reading field. Application: with unobstructed view of
the object without any surrounding objects protruding into the reading plane. One object
with bar code(s) only is inside the reading field during one reading pulse.
•
Differential background:
the distance profile of the reading field background is pro-
grammed (teach-in) in the CLX without any objects present. During the reading process,
the CLX then focuses on the object which it recognizes by comparing it to the distance
profile of the background. Application: with unobstructed view of the object restricted
by other objects that protrude into the reading plane. One object with barcode(s) only
is inside the reading field during one reading pulse.
•
Differential background and tracking:
if several objects with different distances are
positioned in the reading field at the same time (distance conflict), the CLX focuses on
the object that is nearest to but has not exceed its internal focus switchover point.
Application: in OTS operation (applications with tracking by the OMNI Tracking Controller
OTC 400), or stand alone in internal tracking mode.
The distance profile of the background can also be displayed in the "CLV-Setup" program.
The reading field is defined by the autofocus range. The park setting of the focus position,
from which the device focuses for each read, can be specified in addition to a time and/or
position-related delay (timeout or hysteresis). If necessary, an offset can be defined for the
focus position to be set by the measurement. The depth of field, which radiates in the direc-
tion of the scan line and is caused by the V-principle of the beam deflection, is optimized as
a result (
Fig. 3-3:
Optimization the depth of field for the object
Optimum focus position:
measured distance plus offset for maximum
Measured distance
Depth of field (DOF)
